1. Field of the Invention
The present invention relates to an endoscopic high-frequency knife which is inserted into a treatment tool insertion channel of an endoscope to be used as a surgical instrument for an endoscopic mucosal resection (EMR), and the like.
2. Description of the Related Art
A technique of peeling a resection part (e.g., an affected part) with the use of an endoscopic high-frequency knife by firstly injecting physiological saline, or the like, into a submucosa under the resection part to swell (raise) the resection part and subsequently cutting the root of the swelled resection part with the use of the endoscopic high-frequency knife is known in the art as an endoscopic mucosal resection (EMR). As an endoscopic high-frequency knife suitable for the use of such a surgical technique, an endoscopic high-frequency knife to which a high-frequency cutting electrode is installed so that an outer surface of the high-frequency cutting electrode is exposed at a side surface of the insulating flexible sheath in the vicinity of the end thereof is known in the art. This type of endoscopic high-frequency knife is disclosed in Japanese utility model gazette No. 61-7694.
FIG. 7 shows a state in which an endoscopic mucosal resection is performed with the use of a conventional endoscopic high-frequency knife such as that mentioned above. In this state, the root of a swelled resection part 100 of a mucosa is sectioned by a high-frequency cutting electrode 2 in an energized state thereof by swinging the end of a flexible sheath 1, which projects from the distal end of a treatment tool insertion channel of an endoscope (not shown), by manipulating a manual operation portion of the endoscope.
However, in the case where the swelled resection part 100 is greater than the high-frequency cutting electrode 2 as shown in FIG. 7, the swelled resection part 100 cannot be resected completely by a single swing of the end of the flexible sheath 1, and accordingly, it is necessary to swing the end of the flexible sheath 1 repeatedly while gradually changing the incisional position after returning the flexile sheath 1 to its initial position.
However, since the flexible sheath 1 may hit the swelled resection part 100 if one tries to return the flexible sheath 1 directly to its initial position after partly resection the swelled resection part 100 with the high-frequency cutting electrode 2, the endoscope needs to be manipulated so as to return the flexible sheath 1 to its original position in an indirect manner to prevent the flexible sheath 1 from hitting the swelled resection part 100. Hence, it is very troublesome to set the flexible sheath 1 precisely at the subsequent point of commencement of the resection operation.